1. Technical Field
The present invention relates generally to electronic packaging technology and, more particularly, to a modular package for housing unpackaged millimeter wave and microwave devices.
2. Discussion
Unpackaged millimeter wave or microwave devices, or integrated circuits such as Gallium Arsenide (GaAs) MIMIC chips, are those without their associated interconnections, terminations and heat sinks commonly included with standard prepackaged devices. Present technology for housing these devices for interconnection into various application circuits involves the placement of such devices inside hermetically sealed packages. Metallic probes, typically in the form of metal wires, are commonly used to interconnect the unpackaged device, sealed inside the package, to the remainder of the application circuit. Since these devices operate in microwave frequencies, square channel waveguides are often connected to the outside of the package, surrounding the protruding wires, to capture RF signals. These signals are then transmitted through the wire to a separate interface to the chip inside the package. The metallic wires pass through oversized openings in the walls of the package and glass beads are typically employed to seal the wires within the openings.
There are numerous disadvantages to such a configuration, however, the first being the number of separate parts necessary. Also, it is difficult to hermetically seal the probe within the package wall in order to effectively hermetically seal the chip within the package. The glass beads tend to crack under pressure, making such packaging useless. Also, the glass beads employed in packages of this type are difficult to manufacture due to a large number of variations or defects possible therein including surface and subsurface bubbles, cracks, chip outs, improper glass climb and glass overflow and underflow. These packages also have limited electrical performance due to high VSWR and transmission losses.
There is, therefore, a need for a hermetically sealable package for unpackaged millimeter wave and microwave devices which is reliable and simple to manufacture. This package should minimize mechanical interconnection as well as volume, weight and cost. The probe employed should also be designed to minimize electrical discontinuities and resulting VSWR and transmission losses.